| Message ID | 1445420863-1476-1-git-send-email-dh.herrmann@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: David Herrmann <dh.herrmann@gmail.com> Date: Wed, 21 Oct 2015 11:47:43 +0200 > Currently, NETLINK_LIST_MEMBERSHIPS grabs the netlink table while copying > the membership state to user-space. However, grabing the netlink table is > effectively a write_lock_irq(), and as such we should not be triggering > page-faults in the critical section. > > This can be easily reproduced by the following snippet: > int s = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); > void *p = mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); > int r = getsockopt(s, 0x10e, 9, p, (void*)((char*)p + 4092)); > > This should work just fine, but currently triggers EFAULT and a possible > WARN_ON below handle_mm_fault(). > > Fix this by reducing locking of NETLINK_LIST_MEMBERSHIPS to a read-side > lock. The write-lock was overkill in the first place, and the read-lock > allows page-faults just fine. > > Reported-by: Dmitry Vyukov <dvyukov@google.com> > Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Applied and queued up for -stable, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 8f060d7..2389602 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2371,7 +2371,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname, int pos, idx, shift; err = 0; - netlink_table_grab(); + netlink_lock_table(); for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) { if (len - pos < sizeof(u32)) break; @@ -2386,7 +2386,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname, } if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen)) err = -EFAULT; - netlink_table_ungrab(); + netlink_unlock_table(); break; } case NETLINK_CAP_ACK:
Currently, NETLINK_LIST_MEMBERSHIPS grabs the netlink table while copying the membership state to user-space. However, grabing the netlink table is effectively a write_lock_irq(), and as such we should not be triggering page-faults in the critical section. This can be easily reproduced by the following snippet: int s = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); void *p = mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); int r = getsockopt(s, 0x10e, 9, p, (void*)((char*)p + 4092)); This should work just fine, but currently triggers EFAULT and a possible WARN_ON below handle_mm_fault(). Fix this by reducing locking of NETLINK_LIST_MEMBERSHIPS to a read-side lock. The write-lock was overkill in the first place, and the read-lock allows page-faults just fine. Cc: <stable@vger.kernel.org> # 4.2+ Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> --- net/netlink/af_netlink.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)